1. Field of the Invention
This invention relates to a silver halide photographic light-sensitive element and particularly to a silver halide photographic light-sensitive element having a panchromatic sensitiveness upon "flash exposure" and in this case, the term "flash exposure" means one defined in the following description.
2. Description of the Prior Art
In this age of information, various systems have been developed and studied in order to attain quick transmission of information. For example, there are a press facsimile system for quickly transmitting manuscripts for a newspaper to a distant place, a high speed type photo-composing system in order to quickly set up in type, and a cathode ray tube display system for indicating information provided from an electronic computer as characters or patterns.
In machinery and tools for use in these quick information transmitting systems, a short time exposure of less than one-hundred thousandth second, particularly about one-millionth second is mostly adopted. In recent years, the demand for light-sensitive elements employed in such machinery and tools as mentioned above becomes particularly remarkable.
For the light sources employed in these machinery and tools, there are a xenon flash light source and a cathode ray light source other than a combination of a light source of a high illumination intensity such as a xenon-arc lamp and a high pressure mercury-arc lamp with a high speed shutter. In these light sources, such a type of cathode ray tube having particularly fluorescent material of a short after glow period and known generally as a flying spot use is employed. For example, various fluorescent materials such as so-called "P-11," "P-16," "P-22," "P-22D," "P-24," and the like are employed, respectively. In these fluorescent materials, it is generally known that P-11 has the maximum spectroscopic energy distribution of luminescence in a wavelength of 460 nonameters (hereinafter referred to simply as "nm"); the maximum of P-16 is in a wavelength of 385 nm; the maximum of P-24, 520 nm; the maxima of P-22D, 525 nm and 638 nm; other than 450 nm; and the maxima of P-22, 675 nm, other than 620 nm, respectively. For light-sensitive elements in which the above-mentioned various fluorescent materials are employed and which are adopted for recording an image on a cathode ray tube, it is required to impart thereto a panchromatic sensitivity broadened to the end of the red region (about 700 nm).
On the other hand, a light in a region of a comparatively wide wavelength radiates in the case when a xenon flash light source or xenon-arc light source is employed. However, the light emitted from a light source forms an image on the light-sensitive surface of a light-sensitive element through an optical system comprising a condenser lens, negative matrix, main lens, prism, reflector, and the other special lenses or prisms for converting characters. Therefore, concerning the light reaching the light-sensitive surface of the element, light of a short wavelength is absorbed much more than that of a wavelength by the above-mentioned optical system, so that the ratio of the light having a wavelength of from ultraviolet light to blue light decreases while the ratio of the light of a long wavelength increases. For this reason, a spectral sensitization becomes indispensable in order to elevate the sensitivity of the light-sensitive element.
The after-glow period of the luminescence of the above-described cathode ray tube is short, for example, from about one-ten millionth second to one-hundred thousandth second, and with respect to a xenon flash lamp, those having substantially the same short luminescent period as in the above cathode ray tube are mostly employed. In the present invention, a short period exposure by such kinds of light sources as mentioned above is defined as a "flash exposure."
In the case of a high pressure mercury-arc lamp, three bright lines existing in a range of from 300 nm to 370 nm and the lights of 405 nm and 436 nm are ineffective, similarly as in the case of the above xenon lamp, whereas bright lines existing in wavelengths of 546 nm and 577 nm are more effectively utilized than those in the former case. Therefore, a spectral sensitization becomes indispensable in order to elevate the sensitivity of a light-sensitive element.